Two new U-Pb ages of 3448 ± 19 Ma and 3527 ± 17 Ma were obtained on zircons from the Older Metamorphic Tonalite Gneisses (OMTG), Singhbhum North Orissa Craton, Eastern India. These dated TTG-type OMTG gneisses are from the least studied northern area of the Singhbhum Craton. They occur as enclaves in the Singhbhum granite batholith (SBG), emplaced during two distinct periods: from 3440 to 3330 Ma (SBG-A) and from 3200 to 3050 Ma (SBG-B). The U-Pb age of 3448 ± 19 Ma age is close to the older SBG-A phase. The U-Pb age of 3527 ± 17 Ma could corresponds to an older intrusive or inherited from a xenocryst population. Dacitic lava from the southern BIF-bearing Iron Ore Group (IOG) greenstone belt has been recently dated at 3506 ± 2.3 Ma suggesting that it is older than both phases of the SBG. It is thus possible that the metasedimentary rocks of the Older Metamorphic Group (OMG), occurring as enclaves in both OMTG and SBG suites, might be partly derived from the IOG rocks.

抄録全体を表示

The variation in environmental quality of Ondo coast between seasons and sites were evaluated using principal component analysis (PCA). Seventeen metals were analysed in water and sediments with five anionic components further evaluated in water samples. The dry season concentrations of parameter and their degree of variation are higher than that of wet season. PCA of sediments revealed four parameter clusters and five clusters for water based on related sources of input, biogeochemical reactions or effects of physical conditions which are useful means of managing pollution when understood. The concentrations of sediment parameters were higher while their variations are narrower than for water parameters making sediment a veritable tool in coastal pollution monitoring. Mg is the most abundant metal in the sediment while Na and chloride are the most prominent in water. The incursion of saline water therefore plays a major role in the dispersion of pollutants and the water-sediment chemistry of the coast. The spatial variation based on the sediment parameters are much conservative than the water-based. Overall, site 9 and 10 were distinct from the others while sites 1, 2, 3 related perfectly playing important roles in the sourcing and chemistry of pollutants in the coast.

抄録全体を表示

The temporal and vertical distributions of dissolved organic matter in two Chinese eutrophic lakes (Lake Hongfeng and Lake Baihua) were investigated by measuring dissolved organic carbon (DOC), chlorophyll a (Chl a) concentrations and excitation emission matrix (EEM). DOC concentrations were almost similar in those two lakes, but higher (169-330 μM C, average 223 ± 36 μM C) in the epilimnion (0-8 m), and lower (151-303 μM C, 193 ± 25 μM C) in the hypolimnion (10-25 m). Five fluorescence peaks (peaks M and A of fulvic acid-like; peak C of fulvic acid-like or autochthonous DOM-like; peaks T and T_UV of tryptophan-like components, respectively) were observed in the lake waters, indicating various sources of fluorescent dissolved organic matter in lakes. The fluorescence intensities of those peaks decreased (3-61%) in the epilimnion during the summer stratification period compared to hypolimnion. Chl a concentrations were 2.7-65.5 μg l^-1 in the epilimnion and 1.4-41.0 μg l^-1 in hypolimnion with the maximum level in July when water temperature (WT) was the highest of the year. DOC concentrations were significantly correlated with Chl a and WT. Chl a was well correlated with WT in the epilimnion of Lake Hongfeng, suggesting that biological activities might be a major DOC source in the lake waters. DOC concentrations were weakly correlated or not correlated with fulvic acid-like fluorescence in the epilimnion, but they were significantly correlated with tryptophan-like fluorescence, indicating that the tryptophan-like fluorescent material was from new DOM in the lakes during the summer period. But these correlations were often insignificant or absent in the waters of Lake Baihua except peaks T and T_UV, which may be caused by the input of organic contaminants from the industrial activities near Lake Baihua. This study may assist to better understand the sources of lake DOM and the effects of organic matter pollution on the biogeochemical cycling of DOM in lake environments.

抄録全体を表示

The boron concentration and isotopic composition (δ¹¹B) of precipitation collected from December 2002 to March 2006 at three sites on the Japan Sea coast were measured. Those sites have been considerably affected by the long-range transport of air pollutants from the Asian continent during winter and spring when the airflows from the Asian continent are predominant. The boron concentration in the precipitation increased primarily during winter whereas the δ¹¹B decreased during winter or spring. It is assumed that this decrease in δ¹¹B is not associated with a Rayleigh distillation process, because the previous δD values of the precipitation collected at a site on the Japan Sea coast did not decrease in the same manner. A weak correlation (r² = 0.13-0.24, P < 0.01) was observed between δ¹¹B and the nonsea-salt sulfate (nss-SO₄^2-)/B ratio at each site, suggesting that boron in the precipitation originate primarily from two sources. The first source, which is characterized by high δ¹¹B and nss-SO₄^2-/B = 0, is seawater. At the northern site, the enrichment factor for boron in the precipitation relative to seawater approached unity during winter. This implies that much of the boron in the precipitation is derived from unfractionated sea salts rather than gaseous boron evaporated from seawater. The second source is characterized by low δ¹¹B and high nss-SO₄^2-/B ratio. Most of the nss-SO₄^2- in the precipitation originates from anthropogenic combustion activities in the Asian continent based on the previous model calculations. Coal accounts for a major portion of the total primary energy supply in China. Moreover, coal enriches boron and represents generally negative δ¹¹B values. Hence, we propose that the emission of boron from coal burning is the most likely second source. Thus, boron isotopes may be useful as tracers of coal-burning plumes from the Asian continent.

抄録全体を表示

We report the chemical composition of groundwaters—including the first data on the sulfur isotopic composition of dissolved sulfate—from the volcanic aquifers of Mt. Vulture, one of the most important hydrological basins of southern Italy. A total of 27 water samples taken at different altitudes among drilled wells and springs were collected. The majority of groundwaters have a bicarbonate alkaline and bicarbonate alkaline-earth composition. High-salinity waters are sulfate-bicarbonate alkaline in composition. The water-rock interaction process is mainly affected from uprising of CO₂-rich gases which cause an increase of the water acidity promoting basalt weathering with an enrichment in certain chemical species (i.e., Na⁺, Ca²⁺, SO₄^2-) and a high total carbon content. The δ³⁴S values of dissolved sulfate ranging from +4‰ to +8.6‰ can be explained by leaching of volcanites. Higher δ³⁴S values (from 9.6‰ to 10.4‰) detected in a few water springs can be ascribed either to the interaction with the pyroclastic layer rich in feldspathoids, such as haüyna, that have sulfur isotopic compositions up to +10.6‰ or animal manure contamination inducing localized bacterial sulfate reduction with an increase in the δ³⁴S of sulfate. Taking into account that Upper Triassic evaporite deposits have higher δ³⁴S values (from +13.5‰ to +17.4‰,) than those measured in all water samples the dissolution of these deposits could be excluded.

抄録全体を表示

To study the effect of nutrient conditions on the weathering of rock, hydroponic cultivation experiments of two crop plants (soybean and maize) were conducted with two different levels of nutrient supply and the release of elements from rock (basalt and andesite) particles were compared. The rock was encased with two different mesh-sized nets to allow or restrict the free action of fine roots. In the nutrient sufficient experiments approximately 4 times as much amount of the nutrient solution as supplied in the nutrient deficient condition was supplied in total. The release of elements (Ca, Mg, Al, Si, Mn and Fe) was calculated by subtracting the depletion of media from the amount absorbed by the plants, after the appropriate analyses of the media and plants. The experimental results showed that the release of elements in rock depended on nutrient condition. Generally the release of Ca, Mg, Si and Al by the plants was significantly smaller in the nutrient sufficient condition than that in the nutrient deficient condition, whereas Fe showed an opposite change. The difference was the most prominent for both the plants in the experiments with basalt and less clear only in the combination of soybean and andesite. The difference in the release amounts was explainable in terms of physiological requirement of the elements. The plants enhanced the release of elements from rock by secreting H⁺ and/or extending their fine roots to the surface of rock. The effect of the latter action was more important when nutrient was more deficient. When released Si is taken as a measure of rock weathering, basalt and andesite were weathered more rapidly by plants in nutrient deficient conditions.

抄録全体を表示

The saturated and aromatic hydrocarbons isolated from a Cambrian oil (TZ62well) in the central Tarim basin were pyrolyzed in sealed gold tubes to investigate how the gases generated from them would vary in compositions of constituents and their carbon isotopes. The results illustrates that the gases from the cracking of saturates are much drier and more enriched in ¹²C than the gases from the cracking of aromatics at the same levels of thermal maturity. The dryness index of the gases (defined as the volume percentage of C₁ to C_1-5) from the cracking of saturates ranges from 26.2% to 90.6% whereas it is never lower than 60.6% for the gases from the cracking of aromatics throughout the experiment. The methane from the saturates shows a larger carbon isotope change, ranging from -54.8‰ to -35.5‰, than the methane from the aromatics whose carbon isotopes range from -37.4‰ to -32.2‰ throughout the experiment. The above experimental observations indicate that the cracking of crude oils with different bulk compositions could produce gases that have distinct constituents and carbon isotopic compositions.

抄録全体を表示